The invention relates to medical engineering in the field of traumatology and orthopedics, particularlyxe2x80x94to an apparatus for transosseous osteosynthesis.
Known is an apparatus for transosseous osteosynthesis, which apparatus, in order to provide graduated compression and distraction of bone fragments, comprises a detachable repositioning mechanism made in the form of a clamp having through slots on branches to accommodate threaded rods. The clamp is coupled by a threaded connection to an adjusting screw having a handle on one of its ends and a separable adapter that is provided with parallel grooves and mounted on a frame at its other end (see, e.g., USSR Inventor""s Certificate N 1806660 A61, 1993).
A disadvantage of this apparatus is its low reliability. The repositioning mechanism is a two-arm lever mounted on a central supportxe2x80x94an adapter. Sliders with bars, when the apparatus is installed, are disposed with a shift with respect to the central axis, which circumstance, when the adjusting screw is rotated, results in eccentric loads and the seizure effect.
The most similar technical solution is the apparatus for transosseous osteosynthesis, comprising two strips having longitudinal slots, at least three sliders having radial openings disposed in grooves in bracing frames, which frames have openings and are positioned between the strips, at least three bars having a threaded portion on their ends, intended for fixing the bone fragments and disposed in the radial openings of the sliders, three tightening bolts, according to the number of frames, which bolts extend through the slots of the strips and through the openings in the bracing frames, and are intended for compressing and fixing the bracing frames relative to the strips (see, e.g., RU patent 2125417, 1997).
The aforesaid device provides fixation of the bars and enhances reliability in the course of repositioning and during union of the fracture.
However, the aforesaid device does not ensure tool-aided axial compression and distraction of bone fragments. Furthermore, a disadvantage of this device is the highly complicated closed repositioning, because the bone fragments are aligned manually through soft tissues.
The object at the base of the instant invention is to create an apparatus for transosseous osteosynthesis, wherein the presence of a detachable repositioning mechanism for axial compression and distraction of bone fragments, which mechanism eliminates the effect of seizure, will make it possible to improve the quality of the closed repositioning by compression and mechanical fixation of bone fragments, and at the same time will make it possible to simplify the repositioning process using a unit of manual alignment of bone fragments, i.e. improve reliability of the apparatus, accelerate bone union and also, if necessary, lengthen bone tissue.
This object is accomplished in an apparatus for transosseous osteosynthesis, comprising two strips having longitudinal slots, at least three sliders having radial openings, which sliders are disposed in grooves in bracing frames having openings and positioned between the strips, at least three bars having a threaded portion at their ends, intended for fixation of bone fragments and disposed in the radial openings of the sliders, three tightening bolts according to the number of frames, which bolts extend through the strips"" slots and through the openings in the bracing frames, and are intended for compression and fixation of the bracing frames relative to the strips, in that according to the invention, the apparatus further comprises a detachable repositioning mechanism for axial compression and distraction of the bone fragments, which mechanism has a bracing element positioned between the strips"" ends, at least two guiding bars symmetrically secured in the bracing element, a mobile traverse mounted on the guiding bars and having a screw orifice, a lead screw secured in the bracing element whose geometric axis is parallel to the guiding bars"" axes and whose threaded portion interacts with the mobile traverse screw orifice, at least two holders positioned on tightening bolts, two side bars to move the bracing frames, one end of each of the side bars being fixed to the mobile traverse, and the other end secured on a holder by means of a screw clamp.
It is advisable that each holder comprise a hollow body having an inner cylindrical surface, whose axis coincides with that of a corresponding tightening bolt, and a stem on the side surface of the body with an opening, which stem has a threaded portion, washers according to the number of holders and positioned under the head and under the nut of a corresponding tightening bolt, the washers contacting the holder body""s inner cylindrical surface and intended for fixing the holder relative to the tightening bolt, a latch disposed in the holder body and intended for fixing the holder in the direction of axial movement along the tightening bolt.
It is useful that each holder be made in the form of a stepped pin whose axis is shifted relative to that of the tightening bolt, the pin having three steps, the first step comprising a head with an opening to accommodate a tightening bolt, the second step being provided with a radial opening to accommodate a side bar, the third step being provided with a thread to clamp the side bar, the apparatus comprising a bushing disposed on the second step of the pin, which bushing has two opposite radial recesses to accommodate the side bars, the outline of the recesses replicates the side bar outline.
It is advantageous that the lead screw comprise a vernier head.
It is also useful that the apparatus comprise at least one assembly for manual alignment of bone fragments, which assembly has a block with a T-shaped groove, a cylindrical clamping element made in the form of two semicylinders disposed with a gap and interconnected by means of a resilient element, the cylindrical clamping element having a radial cylindrical opening whose axis lies in the gap plane, which radial cylindrical opening is intended to accommodate a bar therein for fixation of the bone fragments, and also having a rectangular opening whose axis is perpendicular to the axis of the cylindrical opening, a screw with a nut, the central portion of the screw having a rectangular bulge with a slot, the head of the screw being disposed in the T-shaped groove of the block, the bulge being disposed in the rectangular opening of the cylindrical clamping element that has a gap, two washers encompassing the cylindrical clamping element from two sides, one of which washers contacting the block, the other washer contacting the nut.
It is advisable that the apparatus comprise an assembly for drawing in and fixing the bone fragments, which assembly is disposed between the strips provided with the longitudinal slots and has a bracing frame with two openings, a tightening bolt extending through the openings in the frame and through the grooves in the strips to secure the bracing frame, a needle having a bulge to draw a bone fragment into a fracture by means of a traction mechanism, which mechanism comprises a turret disposed in the bracing frame and having an annular projection and two mutually perpendicular openings, one of which openings is coaxial with the annular projection, a traction screw extending through the turret opening coaxial with the annular projection and having a head and a longitudinal groove to accommodate the needle therein, a check pin disposed in the traction screw head to fix the needle in a predetermined position in the traction screw, a nut disposed on the annular projection of the turret and interacting with the traction screw by its threaded portion, a bushing with a bead having a thread on the outer surface, which bushing is disposed in the second opening of the turret, a pin also disposed in the second opening of the turret and having a threaded shank disposed in the bushing with the bead, and a radial opening accommodating the traction screw, the longitudinal groove of which traction screw has a key positioned therein to prevent turning, a nut disposed in the beaded bushing and intended to prevent longitudinal movement of the turret relative to the frame, a second nut disposed on the threaded shank of the pin and intended to prevent turning of the turret relative to the frame.
It is advisable that the two strips, at least three bracing frames and the block having the T-shaped groove preferably be made of a material that is permeable to X-radiation.
It is advantageous that a thermosetting composite material including a carbon fibrous filler be used as the material permeable to X-radiation.
It is also useful that the material permeable to X-radiation have a bending strength of at least 500 MPa.